1. Field of the Invention
The present invention relates to a medical stand apparatus capable of holding a medical optical device motionless in a desired spatial position.
2. Description of the Related Art
Cerebral surgery and cardiosurgery include a so-called microsurgery, in which a doctor performs a surgical operation while observing an affected part through an operation microscope serving as a "medical optical device." For use in such microsurgery, there have been proposed various stand apparatuses that can hold a heavy operation microscope and its attachment in a desired spatial position (for example, in Japanese Patent Application Laid-Open (kokai) No. 6-269463). A stand apparatus of this kind is generally composed of a parallel link mechanism which is composed of a plurality of arms. The parallel link mechanism is supported at a predetermined swing pivot. An operation microscope and/or its attachment is held at one end of the parallel link mechanism, and a counterweight is provided at the other end of the parallel link mechanism so as to counterbalance with the operation microscope and/or its attachment. That is, the parallel link mechanism has a balancing structure.
Such a balance-type stand apparatus is installed at a site selected as being optimum for a surgical operation concerned within an operating room, and undergoes balancing adjustment at the site. Since an attachment, such as a side viewer for use by an assistant doctor, a video camera, and the like, are attached to an operation microscope, the position of a counterweight is manually adjusted in accordance with the total weight of the operation microscope and the attachments so as to establish the overall balance of the apparatus.
However, according to such conventional technology, balancing adjustment requires relatively long time, since the position of the counterweight is manually adjusted. Also, when such a stand apparatus is in an imbalanced state, a parallel link mechanism moves to a large extent; thus, there is involved a danger that part of the parallel link may hit a person who is present near the apparatus.
Also, since an operation microscope is located at the side of its supporting device, a sufficient amount of free space is not available around the operation microscope. As a result, movement of the head of a doctor around the operation microscope is limited.